• Keith Busch's avatar
    PCI/LINK: Add Kconfig option (default off) · 2078e1e7
    Keith Busch authored
    e8303bb7 ("PCI/LINK: Report degraded links via link bandwidth
    notification") added dmesg logging whenever a link changes speed or width
    to a state that is considered degraded.  Unfortunately, it cannot
    differentiate signal integrity-related link changes from those
    intentionally initiated by an endpoint driver, including drivers that may
    live in userspace or VMs when making use of vfio-pci.  Some GPU drivers
    actively manage the link state to save power, which generates a stream of
    messages like this:
    
      vfio-pci 0000:07:00.0: 32.000 Gb/s available PCIe bandwidth, limited by 2.5 GT/s x16 link at 0000:00:02.0 (capable of 64.000 Gb/s with 5 GT/s x16 link)
    
    Since we can't distinguish the intentional changes from the signal
    integrity issues, leave the reporting turned off by default.  Add a Kconfig
    option to turn it on if desired.
    
    Fixes: e8303bb7 ("PCI/LINK: Report degraded links via link bandwidth notification")
    Link: https://lore.kernel.org/linux-pci/20190501142942.26972-1-keith.busch@intel.comSigned-off-by: default avatarKeith Busch <keith.busch@intel.com>
    Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
    2078e1e7
Makefile 443 Bytes